<p>This study investigates the synthesis of small-sized nano-spinel copper ferrite powders via the reverse co-precipitation method, specifically examining the influence of an external magnetic field on material properties. X-ray Diffraction (XRD) and Fourier Transform Infrared (FTIR) spectroscopy measurements confirmed the formation of a pure spinel structure, devoid of any detectable impurities. Interestingly, the magnetic field-assisted synthesis significantly increased the crystallite size to&#xa0;11 nm, compared to&#xa0;4 nm&#xa0;for the sample synthesized without a field. N₂ adsorption isotherm measurements with t-curve analysis showed external specific surface areas of 77.423&#xa0;m²g⁻¹ and 30.692&#xa0;m²g⁻¹ for the magnetic field-assisted and magnetic field-free samples, respectively. Barrett-Joyner-Halenda (BJH) analysis further revealed that the magnetic field-synthesized Cu-ferrite nanoparticles exhibited larger average pore volume of 0.3559 cm³g⁻¹ compared to a pore volume of 0.2543 cm³g⁻¹ for the zero-field sample. Magnetic studies demonstrated that the synthesized Cu-ferrite nanoparticles exhibit superparamagnetic behavior, with enhancement in the saturation magnetization of the field-synthesized sample. Furthermore, the optical band gaps of the synthetized Cu-ferrite nanoparticles were found to lie within the visible range measuring 1.90&#xa0;eV for the field sample and 1.98&#xa0;eV for the zero-field sample. The synthesized Cu-ferrite nanoparticles were subsequently evaluated as photocatalytic reagents for the degradation of methylene blue (MB) dye. Crucially, the degradation efficiency was markedly improved for the magnetic field-synthesized Cu-ferrite nanoparticle reaching a value of 98%. The dye degradation process was observed to follow pseudo-first-order kinetics.</p>